The present disclosure relates generally to similar user identifiers.
From an advertiser's perspective, placing an advertisement on a web page may or may not be of interest or useful for the end users viewing the web page. In some systems, the content of a web page may be used to help select more relevant advertisements to be provided with the web page. For example, an advertiser selling golf clubs may advertise on a website devoted to golf, since visitors to the website may share a common interest in golf. Such systems may use keywords located in the text of the website to identify topics discussed on the website.